| US 7,586,649 B2 | ||
| Method and device for compressing image data | ||
| Toshitsugu Yamamoto, Takatsuki (Japan) | ||
| Assigned to Konica Minolta Business Technologies, Inc., Tokyo (Japan) | ||
| Filed on Dec. 23, 2005, as Appl. No. 11/318,046. | ||
| Claims priority of application No. 2004-377575 (JP), filed on Dec. 27, 2004. | ||
| Prior Publication US 2006/0139696 A1, Jun. 29, 2006 | ||
| Int. Cl. G06K 15/00 (2006.01); H04N 1/405 (2006.01); G09G 5/02 (2006.01) | ||
| U.S. Cl. 358—3.13 [358/3.14; 358/3.16; 345/596] | 29 Claims |
| 1. A method for compressing image data that are processed by a pseudo gradation process using a dither pattern, the method
comprising the steps of:
dividing the image data into predetermined areas;
determining whether or not a dot arrangement pattern of the image data in each area matches a dot arrangement pattern that
is obtained by a binarization process that uses imaginary uniform image data and the dither pattern;
determining a representative value concerning density of the image data in the area if the dot arrangement pattern of the
area matches the dot arrangement pattern for the imaginary uniform image data; and
making compressed data by using the determined representative value;
wherein the representative value is a value “a” that satisfies the condition J≧a≧K,
wherein a dot for a given pixel is formed if a density value of the given pixel is smaller than a density value of a pixel
in a corresponding part of the dither pattern, “J” is a minimum value of upper limit density values of pixels of the dither
pattern corresponding to the dots that were formed in the area and “K” is a maximum value of lower limit density values of
pixels of the dither pattern corresponding to dots that were not formed in the area; wherein the steps are performed by a
computer.
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